Re: Diet Recommendations for Endurance Training

[Guest guest]

Below are extracts from a recent article published in the UKSCA

Journal of Strength and Conditioning. Professor Mike Gleeson wrote:

Introduction

There is some evidence that athletes who are training hard or who have

recently competed in endurance race events are at increased risk of

picking up minor illnesses and infections. The most common illnesses

in athletes are viral infections of the upper respiratory tract. In

themselves, these are generally trivial, but they can interrupt

training or cause an athlete to miss, (or under-perform in),

important competitions. Prolonged bouts of strenuous exercise,

particularly if performed without carbohydrate intake, and periods of

hard training with limited recovery and/or inadequate energy intake

may compromise the body's immune system, and high levels of stress

hormones brought on by chronic physical and/or psychological stress

reduce its ability to fight opportunistic infections including colds

and influenza. Acute bouts of strenuous aerobic exercise lasting 90

minutes or more have been shown to result in transient depression of

several aspects of both innate and acquired immunity, including

decreased functional responses of monocytes, neutrophils, natural

killer cells and T and B lymphocytes. It is suggested that such

changes create an " open window " of decreased host protection, during

which viruses and bacteria can gain a foothold, increasing the risk

of developing an infection. Other factors such as psychological

stress, lack of sleep and malnutrition can also depress immunity and

lead to increased risk of infection.

Table 1: Strategies to counter illness risk in athletes

• Diet is important for immune function and many vitamins and

minerals are associated with the ability to fight

infection, particularly vitamin C, vitamin A and zinc. A good, well-

balanced diet should provide all the

necessary vitamins and minerals, but if fresh fruit and vegetables

are not readily available, multivitamin

supplements should be considered.

• Nutritional considerations should emphasize the need for adequate

intakes of fluid, carbohydrate, protein and

micronutrients. Ensuring the recovery of glycogen stores on a day-to-

day basis and consuming carbohydrate

during exercise (about 30-60g of carbohydrate per hour during

exercise seems to be effective), appear to be

ways of minimizing the temporary immunodepression associated with an

acute bout of prolonged exercise and

reduces chances of developing overreaching symptoms.

• The evidence for the benefit of so-called immune-boosting

supplements (e.g. glutamine, echinacea, colostrum)

is weak, though there is some evidence that probiotics and several

antioxidant compounds (e.g. vitamin C,

flavonoids such as quercetin) may be effective in reducing infection

risk.

• Avoid getting a dry mouth, both during competition and at rest;

this can be done by drinking at regular

intervals and maintaining hydration status.

• Never share drink bottles, cutlery or towels and use properly

treated water for consumption.

• Other behavioural/lifestyle changes such as good hygiene practice

(washing hands and brushing teeth

regularly; using an antibacterial mouth rinse), may limit

transmission of contagious illnesses by reducing

exposure to common sources of infection.

• Avoid putting the hands to the eyes and nose (a major route of

viral self-innoculation).

• Keep other life/social/psychological stresses to a minimum and get

regular and adequate sleep.

• Avoid rapid weight loss.

• Before important competitive events, avoid sick people and large

crowds in enclosed spaces when possible.

• Medical support including regular check ups, appropriate

immunization and prophylaxis may be particularly

important for athletes who are at high risk of succumbing to

recurrent infection.

• Vaccinate athletes, and all support staff who are in regular

contact with athletes.

• Be aware of particular vulnerability to infection after training or

competition, especially in the winter months.

• Training should be stopped if the athlete has a fever and/or

systemic symptoms including aching joints and

muscles. It is probably OK to continue training (though at a reduced

load) if the symptoms are all above the

neck.

• Iron supplements should not be taken during periods of infection.

• Team members with infection should be isolated as much as possible

from the rest of the team.

The best evidence supports the implementation of

appropriate rest periods within the training micro-cycle

and the use of a high carbohydrate diet and

carbohydrate ingestion (about 30-60 grams per hour)

during prolonged workouts, which lowers circulating

adrenaline and cortisol levels and delays the

appearance of symptoms of overreaching during

intensive training periods. Several placebo-controlled

studies in runners and cyclists have shown that

carbohydrate ingestion (usually in the form of a

beverage) during prolonged exercise is effective in

attenuating changes in immune function. However,

evidence is currently lacking to demonstrate that this

translates to a reduced incidence of upper respiratory

tract infection (URTI) following competitive events.

While there are many nutritional supplements including

arginine, glutamine, bovine colostrum and whey

protein, vitamin C, probiotics, zinc and herbals such as

echinacea on the market that are claimed to boost

immunity, such claims are often based on

selective evidence of efficacy in animals, in vitro

experiments, children, the elderly or clinical patients in

severe catabolic states and direct evidence for their

efficacy for preventing exercise-induced immune

depression or improving immune system status in

athletes is usually lacking.

======================

Carruthers

Wakefield, UK

>

> ________________________________

>

> From: Supertraining on behalf of gloria_bach

> Sent: Thu 12/18/2008 5:27 PM

> To: Supertraining

> Subject: Re: Diet Recommendations for Endurance

Training

>

>

>

> Thanks Jim,

> The book on Nutrient Timing sounds interesting and I will look into

> it. I do think the URI's might have something to do with what we do

> to ourselves after our workouts and how we fit recovery nutrition

into

> the schedule. It gets more complicated when the athlete works with

> young children (germ transmitters). I got a flu shot this year for

> the first time and I think that may be helping to keep things mild.

> Haven't needed antibiotics since getting the shot.

> Gloria Bach

> Willseyville NY

>

>

> >

> > I remember reading that upper respiratory infections (URI) are

pretty

> > common in endurance athletes. Triathletes, after all, do get run

down.

> >

> > What advice do Supertraining members have for endurance athletes

who

> > have URI issues?

> >

> > I'm a novice in this area - but I've just finished reading two

books

> > on nutrition for athletes and they may be helpful.

> >

> > The book " The Paleo Diet for Athletes " by Loren Cordain and Joe

Friel

> > has a section on diet for endurance training, including what to

eat

> > before, during, and after a race.

> >

> > Also " Nutrient Timing " by Ivy and Portman discusses

> > similar topics.

> >

> > I think both books point to research showing that URI is reduced

when

> > recovery is aided by careful nutrient timing.... but skimming the

> > books I can't find the research references just now.

> >

> > jim lorenz

> > los altos, ca, usa

> >

>